Battery pack temperature control method, device and system for thermal management system

Abstract

Embodiments of the present invention disclose a battery pack temperature control method, device, and system for a thermal management system. The thermal management system includes a refrigerant circuit, a water circuit, and a controller. The refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve, and a battery pack. The control method includes: determining the subcooling degree of the second end of the water-cooled heat exchanger, the superheat degree of the first end of the battery pack, and the superheat degree of the evaporator outlet based on the temperature and pressure of the second end of the water-cooled heat exchanger, the temperature and pressure of the first end of the battery pack, and the temperature and pressure of the evaporator outlet; and determining the target opening of each electronic expansion valve based on the first end temperature, the second end subcooling degree, the first end superheat, and the outlet superheat to control the temperature of the battery pack. The technical solution provided by the embodiment of the present invention can prevent excessive temperature differences between the inlet and outlet of the battery pack and prevent condensation in the battery pack and pipelines.

Description

Technical Field

[0001] Embodiments of the present invention relate to thermal system control technology, and more particularly to a method, device, and system for controlling the temperature of a battery pack in a thermal management system. Background Art

[0002] Battery packs, such as those in thermal management systems, serve as the energy storage and power supply for devices requiring power. Excessively high or low battery pack temperatures during operation can affect the battery pack and even the entire system, necessitating temperature control of the battery pack within the thermal management system.

[0003] Currently, the existing battery pack temperature control method of the thermal management system has the problem of excessive overheating at the battery pack outlet, resulting in a large temperature difference between the battery pack inlet and outlet, and also the problem of condensation in the battery pack and pipelines. Summary of the Invention

[0004] Embodiments of the present invention provide a battery pack temperature control method, device, and system for a thermal management system to prevent excessive temperature differences between the inlet and outlet of the battery pack and to prevent condensation in the battery pack and pipelines.

[0005] In a first aspect, an embodiment of the present invention provides a battery pack temperature control method for a thermal management system, wherein the thermal management system includes a refrigerant circuit, a water circuit, and a controller, the refrigerant circuit including a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve, and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser, and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, and the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger. The first end of the battery pack is in communication with the inlet of the gas-liquid separator, and the outlet of the gas-liquid separator is in communication with the inlet of the compressor. The first electronic expansion valve is located in a pipeline in communication with the second end of the battery pack and is close to the second end of the battery pack. The second electronic expansion valve is located in a pipeline in communication with the inlet of the evaporator and is close to the inlet of the evaporator. The third electronic expansion valve is located in a pipeline in communication with the first end of the battery pack and is close to the first end of the battery pack. The third and fourth ends of the water-cooled heat exchanger are in communication with the water circuit. The compressor and each electronic expansion valve are electrically connected to the controller. The control method is executed by the controller. The control method includes:

[0006] Obtaining the temperature and pressure of the second end of the water-cooled heat exchanger, the temperature and pressure of the first end of the battery pack, and the temperature and pressure of the evaporator outlet; the current operating mode of the thermal management system is a dual cooling mode for the battery and cabin;

[0007] determining a subcooling degree at the second end of the water-cooled heat exchanger, a superheat degree at the first end of the battery pack, and a superheat degree at the outlet of the evaporator based on the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the outlet of the evaporator;

[0008] The target opening of each electronic expansion valve is determined according to the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree and the outlet superheating degree to control the temperature of the battery pack.

[0009] Optionally, determining the target opening of each electronic expansion valve according to the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree, and the outlet superheating degree includes:

[0010] determining a superheat difference between the first end superheat and the target superheat according to the first end superheat and the target superheat, and performing PID control on the superheat difference to obtain a target opening of the first electronic expansion valve;

[0011] determining a subcooling difference between the second end subcooling degree and the target subcooling degree according to the second end subcooling degree and the target subcooling degree, and performing PID control on the subcooling difference to obtain a target opening degree of the second electronic expansion valve;

[0012] The target opening of the third electronic expansion valve is determined according to the pressure at the first end of the battery pack.

[0013] Optionally, determining the target opening of each electronic expansion valve according to the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree, and the outlet superheating degree includes:

[0014] determining a superheat difference between the first end superheat and the target superheat according to the first end superheat and the target superheat, and performing PID control on the superheat difference to obtain a first opening of the first electronic expansion valve;

[0015] determining a subcooling difference between the second end subcooling degree and the target subcooling degree according to the second end subcooling degree and the target subcooling degree, and performing PID control on the subcooling difference to obtain a second opening degree of the first electronic expansion valve;

[0016] determining a target opening of the first electronic expansion valve according to the first opening and the second opening;

[0017] determining a superheat difference between the outlet superheat and the target superheat according to the outlet superheat and the target superheat, and performing PID control on the superheat difference to obtain a target opening of the second electronic expansion valve;

[0018] A target opening of the third electronic expansion valve is determined according to the pressure at the first end of the battery pack.

[0019] Optionally, determining a target opening of the first electronic expansion valve according to the first opening and the second opening includes:

[0020] If the first opening is greater than the second opening, the first opening is used as the target opening of the first electronic expansion valve;

[0021] If the first opening degree is less than or equal to the second opening degree, the second opening degree is used as the target opening degree of the first electronic expansion valve.

[0022] Optionally, determining the target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack includes:

[0023] determining an evaporation temperature at a first end of the battery pack according to a pressure at a first end of the battery pack;

[0024] If the target evaporation temperature in the cabin is lower than the target evaporation temperature of the battery pack, subtracting the first end evaporation temperature from the target evaporation temperature of the battery pack to obtain a temperature difference;

[0025] Performing PID control on the temperature difference to obtain a target opening of the third electronic expansion valve;

[0026] If the target evaporation temperature in the cabin is higher than or equal to the target evaporation temperature of the battery pack, the target opening of the third electronic expansion valve is controlled to be a preset maximum opening.

[0027] Optionally, the water circuit includes an armature assembly, an electronic water pump, a radiator, and a cooling fan; the third end of the water-cooled heat exchanger, the armature assembly, the electronic water pump, and the radiator are sequentially connected; the cooling fan is located on one side of the radiator; and the cooling fan is electrically connected to the controller;

[0028] After determining the target opening degrees of the first electronic expansion valve and the second electronic expansion valve, the method includes:

[0029] When the overheat degree of the first end of the battery pack is greater than a preset overheat threshold, and the first electronic expansion valve fails or the opening degree of the first electronic expansion valve reaches a preset opening degree threshold, controlling the speed of the cooling fan to increase;

[0030] When the speed of the cooling fan increases to a preset speed threshold, controlling the opening of the third electronic expansion valve to decrease;

[0031] When the opening degree of the third electronic expansion valve decreases to a preset opening degree threshold, the speed of the compressor is controlled to decrease.

[0032] Optionally, the refrigerant circuit further includes a fourth electronic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve and a fourth solenoid valve, the fourth electronic expansion valve being located in a pipeline connected to the outlet of the condenser and close to the outlet of the condenser, the first solenoid valve being located in a pipeline connected to the outlet of the compressor and the first end of the water-cooled heat exchanger, the second solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the condenser, the third solenoid valve being located in a pipeline connected to the outlet of the evaporator and the first end of the water-cooled heat exchanger, and the fourth solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the gas-liquid separator; each solenoid valve and each electronic expansion valve being electrically connected to the controller;

[0033] In the battery and cabin dual cooling mode, the first solenoid valve and the fourth solenoid valve are turned on, the second solenoid valve, the third solenoid valve and the fourth electronic expansion valve are turned off.

[0034] In a second aspect, an embodiment of the present invention provides a battery pack temperature control device of a thermal management system, wherein the thermal management system includes a refrigerant circuit, a water circuit, and a controller, wherein the refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve, and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser, and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, and the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger. The first end of the battery pack is in communication with the inlet of the gas-liquid separator, and the outlet of the gas-liquid separator is in communication with the inlet of the compressor. The first electronic expansion valve is located in a pipeline connected to the second end of the battery pack and is close to the second end of the battery pack. The second electronic expansion valve is located in a pipeline connected to the inlet of the evaporator and is close to the inlet of the evaporator. The third electronic expansion valve is located in a pipeline connected to the first end of the battery pack and is close to the first end of the battery pack. The third and fourth ends of the water-cooled heat exchanger are in communication with the water circuit. The compressor and each electronic expansion valve are electrically connected to the controller, and the control device is integrated into the controller. The control device includes:

[0035] a parameter acquisition module, configured to acquire the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the evaporator outlet; wherein the current operating mode of the thermal management system is a dual cooling mode for the battery and the cabin;

[0036] a parameter determination module, configured to determine a subcooling degree at the second end of the water-cooled heat exchanger, a superheat degree at the first end of the battery pack, and an outlet superheat degree of the evaporator based on the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the outlet of the evaporator;

[0037] An opening determination module is used to determine the target opening of each electronic expansion valve based on the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree and the outlet superheating degree, so as to control the temperature of the battery pack.

[0038] In a third aspect, an embodiment of the present invention provides a thermal management system, comprising: a refrigerant circuit, a water circuit and a controller, wherein the refrigerant circuit comprises a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger, and the battery pack The first end is connected to the inlet of the gas-liquid separator, the outlet of the gas-liquid separator is connected to the inlet of the compressor, the first electronic expansion valve is located in the pipeline connected to the second end of the battery pack and is close to the second end of the battery pack, the second electronic expansion valve is located in the pipeline connected to the inlet of the evaporator and is close to the inlet of the evaporator, the third electronic expansion valve is located in the pipeline connected to the first end of the battery pack and is close to the first end of the battery pack, the third end and the fourth end of the water-cooled heat exchanger are connected to the water circuit; the compressor and each electronic expansion valve are electrically connected to the controller, and the control device as described in the second aspect is integrated in the controller.

[0039] Optionally, the refrigerant circuit further includes a fourth electronic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve and a fourth solenoid valve, the fourth electronic expansion valve being located in a pipeline connected to the outlet of the condenser and close to the outlet of the condenser, the first solenoid valve being located in a pipeline connected to the outlet of the compressor and the first end of the water-cooled heat exchanger, the second solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the condenser, the third solenoid valve being located in a pipeline connected to the outlet of the evaporator and the first end of the water-cooled heat exchanger, and the fourth solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the gas-liquid separator; each solenoid valve and each electronic expansion valve being electrically connected to the controller;

[0040] The water circuit includes an armature assembly, an electronic water pump, a radiator and a cooling fan. The third end of the water-cooled heat exchanger, the armature assembly, the electronic water pump, the radiator and the fourth end of the water-cooled heat exchanger are connected in sequence. The cooling fan is located on one side of the radiator; the cooling fan is electrically connected to the controller.

[0041] The battery pack temperature control method, device and system of the thermal management system provided by the embodiment of the present invention, the thermal management system includes a refrigerant circuit, a water circuit and a controller, the refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger, the first end of the battery pack is connected to the inlet of the gas-liquid separator, the outlet of the gas-liquid separator is connected to the inlet of the compressor, the first electronic expansion valve is located in a pipeline connected to the second end of the battery pack and is close to the second end of the battery pack, the second electronic expansion valve is located in a pipeline connected to the inlet of the evaporator and is Near the inlet of the evaporator, the third electronic expansion valve is located in a pipeline connecting the first end of the battery pack and the inlet of the gas-liquid separator and is close to the first end of the battery pack, and the third and fourth ends of the water-cooled heat exchanger are connected to the water circuit; the compressor and each electronic expansion valve are electrically connected to the controller, and the control method is executed by the controller, and the control method includes: obtaining the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the temperature and pressure of the evaporator outlet; the current working mode of the thermal management system is the dual cooling mode of the battery and the cabin; according to the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the temperature and pressure of the evaporator outlet, the second end subcooling of the water-cooled heat exchanger, the first end superheat of the battery pack and the outlet superheat of the evaporator are determined; according to the first end temperature, the second end subcooling, the first end superheat and the outlet superheat, the target opening of each electronic expansion valve is determined to control the temperature of the battery pack. The battery pack temperature control method, device and system of the thermal management system provided in the embodiments of the present invention control the opening of each electronic expansion valve to control the refrigerant flow rate flowing through each electronic expansion valve, and further control the refrigerant flow rate entering and flowing out of the battery pack and the evaporation temperature of the battery pack, thereby controlling the outlet superheat of the battery pack, preventing excessive temperature difference between the inlet and outlet of the battery pack due to excessive overheating of the battery pack outlet, and preventing condensation in the battery pack and pipelines due to excessively low evaporation temperature of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of a battery pack temperature control method of a thermal management system provided in Example 1 of the present invention;

[0043] Figure 2 This is a schematic structural diagram of a thermal management system provided by Embodiment 1 of the present invention;

[0044] Figure 3 This is a flow chart of a battery pack temperature control method of a thermal management system provided in Embodiment 2 of the present invention;

[0045] Figure 4 This is a schematic structural diagram of a thermal management system in a dual cooling mode of battery and cabin provided by the second embodiment of the present invention;

[0046] Figure 5 This is a flow chart of a battery pack temperature control method of a thermal management system provided in Example 3 of the present invention;

[0047] Figure 6 This is a schematic diagram of an opening and flow rate provided in the third embodiment of the present invention;

[0048] Figure 7 This is a structural block diagram of a battery pack temperature control device of a thermal management system provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0050] Example 1

[0051] Figure 1 This is a flow chart of a battery pack temperature control method of a thermal management system provided in Example 1 of the present invention. Figure 2 This is a schematic diagram of the structure of a thermal management system provided by the first embodiment of the present invention. This embodiment can be applied to aspects such as controlling the battery pack temperature of the thermal management system. Figure 1 and Figure 2The thermal management system includes a refrigerant circuit 100, a water circuit 200 and a controller (not shown in the figure). The refrigerant circuit 100 includes a compressor 10, a condenser 20, an evaporator 30, a water-cooled heat exchanger 40, a gas-liquid separator 50, a first electronic expansion valve 61, a second electronic expansion valve 62, a third electronic expansion valve 63 and a battery pack 70; the outlet of the compressor 10 is connected to the first end of the water-cooled heat exchanger 40, the inlet of the condenser 20, and the first end of the battery pack 70, the second end of the water-cooled heat exchanger 40 is connected to the outlet of the condenser 20, the outlet of the condenser 20 is connected to the inlet of the evaporator 30 and the second end of the battery pack 70, the outlet of the evaporator 30 is connected to the first end of the battery pack 70 and the first end of the water-cooled heat exchanger 40, and the first end of the battery pack 70 is connected to the gas-liquid separator 50. The inlet of the separator 50 is connected, the outlet of the gas-liquid separator 50 is connected to the inlet of the compressor 10, the first electronic expansion valve 61 is located in a pipeline connected to the second end of the battery pack 70 and is close to the second end of the battery pack 70, the second electronic expansion valve 62 is located in a pipeline connected to the inlet of the evaporator 30 and is close to the inlet of the evaporator 30, the third electronic expansion valve 63 is located in a pipeline connected to the first end of the battery pack 70 and the inlet of the gas-liquid separator 50 and is close to the first end of the battery pack 70, the third end and the fourth end of the water-cooled heat exchanger 40 are connected to the water circuit 200; the compressor 10 and each electronic expansion valve are electrically connected to the controller; the method is executed by the controller of the thermal management system, and the controller can be implemented in the form of software and / or hardware. The method specifically includes the following steps:

[0052] Step 110: Obtain the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the evaporator outlet; the current operating mode of the thermal management system is the battery and cabin dual cooling mode.

[0053] Specifically, taking the application of thermal management system in new energy vehicles as an example, the cabin refers to the passenger compartment of the new energy vehicle. Figure 2 As shown, the second end of the water-cooled heat exchanger, the first end of the battery pack and the evaporator outlet are respectively provided with pressure and temperature sensors PT2, PT4 and PT1. The pressure and temperature sensors can collect the pressure and temperature at their respective locations. The battery pack temperature control device of the thermal management system is electrically connected to each pressure and temperature sensor PT1-PT5 to obtain the corresponding temperature and pressure.

[0054] Step 120: Determine the second end supercooling of the water-cooled heat exchanger, the first end superheat of the battery pack, and the outlet superheat of the evaporator based on the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the outlet temperature and pressure of the evaporator.

[0055] Specifically, the battery pack's first-end overheat is determined based on the battery pack's first-end temperature and pressure (in dual-battery and cabin cooling mode, the battery pack's first-end overheat is the battery pack's outlet overheat). The water-cooled heat exchanger's second-end subcooling is determined based on the water-cooled heat exchanger's second-end temperature and pressure (equivalent to the battery pack's second-end temperature and pressure). (Equivalent to the battery pack's second-end subcooling; in dual-battery and cabin cooling mode, the battery pack's second-end subcooling is the battery pack's inlet subcooling.) The evaporator's outlet superheat is determined based on the evaporator's outlet temperature and pressure. The process of determining subcooling or superheat based on temperature and pressure can be referenced to existing techniques and will not be elaborated upon here.

[0056] Step 130 : Determine the target opening of each electronic expansion valve according to the first-end pressure, the second-end subcooling degree, the first-end superheating degree, and the outlet superheating degree to control the temperature of the battery pack.

[0057] Specifically, the target opening of the third electronic expansion valve is determined based on the pressure at the first end of the battery pack. The superheat difference between the target superheat and the first-end superheat is determined based on the first-end superheat and the corresponding target superheat. The subcooling difference between the target subcooling and the second-end subcooling is determined based on the second-end subcooling and the target subcooling. The target opening of the first electronic expansion valve is determined based on the superheat difference, and the subcooling difference is subjected to PID control to determine the target opening of the second electronic expansion valve. Alternatively, the target opening of the first electronic expansion valve is determined based on the superheat difference and the subcooling difference, and the target opening of the second electronic expansion valve is determined based on the outlet superheat and the corresponding target superheat.

[0058] The battery pack temperature control method of the thermal management system provided in this embodiment controls the opening of each electronic expansion valve to control the refrigerant flow rate flowing through each electronic expansion valve, and further controls the refrigerant flow rate entering and flowing out of the battery pack and the evaporation temperature of the battery pack, thereby controlling the outlet superheat of the battery pack, preventing excessive temperature difference between the inlet and outlet of the battery pack due to excessive overheating of the battery pack outlet, and preventing condensation in the battery pack and pipelines due to excessively low evaporation temperature of the battery pack.

[0059] Example 2

[0060] Figure 3 This is a flow chart of a method for controlling the battery pack temperature of a thermal management system provided in the second embodiment of the present invention. This embodiment is applicable to controlling the battery pack temperature of the thermal management system. The structure of the thermal management system is as follows: Figure 2 As shown, the specific description can refer to the first embodiment, which will not be repeated here; the method is executed by a controller of the thermal management system, and the controller can be implemented in the form of software and / or hardware. The method specifically includes the following steps:

[0061] Step 210: Obtain the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the evaporator outlet; the current operating mode of the thermal management system is the battery and cabin dual cooling mode.

[0062] Specifically, when the operating mode of the thermal management system is the dual cooling mode of the battery and the cabin, the temperature and pressure of the second end of the water-cooled heat exchanger, the temperature and pressure of the first end of the battery pack, and the temperature and pressure of the evaporator outlet are obtained. The specific acquisition process can be referred to the description of the above embodiment and will not be repeated here.

[0063] Step 220: Determine the second end supercooling of the water-cooled heat exchanger, the first end superheat of the battery pack, and the outlet superheat of the evaporator based on the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the outlet temperature and pressure of the evaporator.

[0064] The second-end subcooling degree of a water-cooled heat exchanger is the difference between the second-end temperature of the water-cooled heat exchanger and the saturation temperature corresponding to the pressure at the second end of the water-cooled heat exchanger. The first-end superheat degree of a battery pack is the difference between the first-end temperature of the battery pack and the saturation temperature corresponding to the pressure at the first end of the battery pack. The outlet superheat degree of an evaporator is the difference between the outlet temperature of the evaporator and the saturation temperature corresponding to the pressure at the evaporator.

[0065] Step 230: Determine the superheat difference between the target superheat and the first end superheat according to the first end superheat and the target superheat, and perform PID control on the superheat difference to obtain the target opening of the first electronic expansion valve.

[0066] Specifically, the target superheat is subtracted from the first end superheat, and the difference is used as the superheat difference. The value obtained by proportional integral differential operation, i.e. PID control, of the superheat difference is used as the target opening of the first electronic expansion valve.

[0067] Step 240: Determine a subcooling difference between the target subcooling and the second-end subcooling according to the second-end subcooling and the target subcooling, and perform PID control on the subcooling difference to obtain a target opening of the second electronic expansion valve.

[0068] Specifically, the subcooling difference is calculated by subtracting the target subcooling degree corresponding to the second electronic expansion valve from the subcooling degree at the second end. PID control is then performed on this subcooling difference to determine the target opening of the second electronic expansion valve. For example, the target subcooling degree corresponding to the second electronic expansion valve is 10°C (calibration value 7). This calibration value is used to control the refrigerant flowing through the second electronic expansion valve to a pure liquid state. Excessively large or small values ​​can affect system performance, and the range is 4-10°C.

[0069] Step 250: Determine the target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack.

[0070] Specifically, the evaporation temperature at the first end of the battery pack is determined based on the pressure at the first end of the battery pack. The first-end evaporation temperature is the saturation temperature corresponding to the first-end pressure and can be determined by looking up a table that records the saturation temperature corresponding to the pressure. If the target evaporation temperature in the cabin is lower than the target evaporation temperature of the battery pack (the target evaporation temperature is the outlet evaporation temperature of the battery pack), the first-end evaporation temperature is subtracted from the target evaporation temperature of the battery pack to obtain a temperature difference. PID control is then performed on this temperature difference to determine the target opening of the third electronic expansion valve. If the target evaporation temperature in the cabin is higher than or equal to the target evaporation temperature of the battery pack, the target opening of the third electronic expansion valve is controlled to a preset maximum opening. For example, the target evaporation temperature in the cabin is [3, 5]°C (calibration value 9). Calibration value 9 is the switching condition for the closed-loop PID control of the third electronic expansion valve, which is set to 2°C and initially set to [3, 5]°C. The third electronic expansion valve acts as a secondary throttling device, controlling the battery pack's evaporation temperature to the target evaporation temperature, such as 20-25°C, thereby preventing condensation and frosting on the battery and refrigerant circuits.

[0071] Further, refer to Figure 2 The refrigerant circuit also includes a fourth electronic expansion valve 64, a first solenoid valve 81, a second solenoid valve 82, a third solenoid valve 83 and a fourth solenoid valve 84. The fourth electronic expansion valve 64 is located in the pipeline connected to the outlet of the condenser 20 and is close to the outlet of the condenser 20. The first solenoid valve 81 is located in the pipeline connecting the outlet of the compressor 10 and the first end of the water-cooled heat exchanger 40. The second solenoid valve 82 is located in the pipeline connecting the first end of the battery pack 70 and the inlet of the condenser 20. The third solenoid valve 83 is located in the pipeline connecting the outlet of the evaporator 30 and the first end of the water-cooled heat exchanger 40. The fourth solenoid valve 84 is located in the pipeline connecting the first end of the battery pack 70 and the inlet of the gas-liquid separator 50. A blower 31 is provided on the side of the evaporator 30 away from the condenser 20. Each solenoid valve and each electronic expansion valve is electrically connected to the controller.

[0072] For example, Figure 4 This is a schematic diagram of the structure of a thermal management system in a dual cooling mode of battery and cabin provided by the second embodiment of the present invention. Figure 4 In the dual cooling mode of battery and cabin, the on-off status of each solenoid valve is: the first solenoid valve 81 is on, the fourth solenoid valve 84 is on, the second solenoid valve 82 is off, the third solenoid valve 83 is off, and the fourth electronic expansion valve 64 is off. The refrigerant flow direction of the refrigerant circuit is as follows: Figure 4In the direction of the middle arrow, the refrigerant enters the gas-liquid separator 50 and enters the compressor 10, where it is compressed into a high-temperature, high-pressure gas. The high-temperature, high-pressure gas then flows out of the water-cooled heat exchanger 40 as a liquid refrigerant. One path of the liquid refrigerant passes through the first electronic expansion valve 61 for throttling and expansion to a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant evaporates and exchanges heat in the battery pack 70, becoming a gas or a gas-liquid mixed state. The other path of the liquid refrigerant passes through the second electronic expansion valve 62 for throttling and expansion to a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant evaporates and exchanges heat in the evaporator 30, becoming a gas or a gas-liquid mixed state. The low-temperature, low-pressure refrigerant then mixes with the refrigerant exiting the battery pack 70 and enters the gas-liquid separator 50, finally entering the next cycle. Furthermore, the control method of this embodiment is applicable during a system cold start, ensuring that the battery pack is prioritized. The battery pack outlet has a certain degree of superheat but maintains a low level, making it suitable for prioritizing the battery pack's needs when cooling capacity is insufficient, such as during the system startup phase.

[0073] It should be noted that the above-mentioned preset values ​​and target values ​​are determined according to actual control requirements and are not limited here.

[0074] The battery pack temperature control method for a thermal management system provided in this embodiment determines the target opening of a first electronic expansion valve based on the temperature and pressure at the first end of the battery pack, and determines the target opening of a second electronic expansion valve based on the temperature and pressure at the second end of a water-cooled heat exchanger. By controlling the openings of the first and second electronic expansion valves, the refrigerant flow rate into and out of the battery pack is controlled, thereby controlling the battery pack outlet superheat and preventing a large temperature difference between the inlet and outlet of the battery pack caused by excessive outlet superheat. Furthermore, the target opening of a third electronic expansion valve is determined based on the pressure at the first end of the battery pack. Specifically, the evaporation temperature at the first end of the battery pack is determined based on the pressure at the first end of the battery pack. The target opening of the third electronic expansion valve is determined based on the target evaporation temperature in the cabin and the evaporation temperature at the first end of the battery pack, thereby controlling the evaporation temperature of the battery pack and preventing condensation in the battery pack and piping due to excessively low evaporation temperature.

[0075] Example 3

[0076] Figure 4 This is a flow chart of a method for controlling the temperature of a battery pack of a thermal management system provided by the third embodiment of the present invention. This embodiment is applicable to controlling the temperature of a battery pack of a thermal management system. The structure of the thermal management system is as follows: Figure 2 As shown, the specific description can refer to the above embodiment and will not be repeated here. The method is executed by a controller of the thermal management system, and the controller can be implemented in the form of software and / or hardware. The method specifically includes the following steps:

[0077] Step 310: Obtain the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the evaporator outlet; the current operating mode of the thermal management system is the battery and cabin dual cooling mode.

[0078] The specific process of obtaining each temperature and pressure can be referred to the description of the above embodiment and will not be repeated here.

[0079] Step 320: Determine the second end supercooling of the water-cooled heat exchanger, the first end superheat of the battery pack, and the outlet superheat of the evaporator based on the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the outlet temperature and pressure of the evaporator.

[0080] Step 330: Determine a superheat difference between the target superheat and the first-end superheat according to the first-end superheat and the target superheat, and perform PID control on the superheat difference to obtain a first opening of the first electronic expansion valve.

[0081] The superheat at the first end of the battery pack is the difference between the temperature at the first end of the battery pack and the saturation temperature corresponding to the pressure at the first end of the battery pack. Specifically, the target superheat is subtracted from the first end superheat to obtain the superheat difference. The value obtained by performing a proportional-integral-differential calculation on the superheat difference is used as the first opening degree of the first electronic expansion valve. For example, the target superheat corresponding to the first end superheat is 5°C (calibration value 2).

[0082] Step 340: Determine a subcooling difference between the target subcooling and the second-end subcooling according to the second-end subcooling and the target subcooling, and perform PID control on the subcooling difference to obtain a second opening of the first electronic expansion valve.

[0083] Specifically, a subcooling difference is obtained by subtracting the target subcooling degree corresponding to the first electronic expansion valve from the subcooling degree at the second end. PID control is then performed on the subcooling difference to obtain the second opening degree of the first electronic expansion valve. For example, the target subcooling degree corresponding to the first electronic expansion valve is 5°C (calibration value 1).

[0084] Step 350: Determine a target opening of the first electronic expansion valve according to the first opening and the second opening.

[0085] Specifically, if the first opening is greater than the second opening, the first opening is used as the target opening of the first electronic expansion valve; if the first opening is less than the second opening, the second opening is used as the target opening of the first electronic expansion valve.

[0086] Step 360: Determine the superheat difference between the target superheat and the outlet superheat based on the outlet superheat and the target superheat, and perform PID control on the superheat difference to obtain the target opening of the second electronic expansion valve.

[0087] Specifically, the superheat difference is calculated by subtracting the target superheat from the outlet superheat. For example, the outlet superheat corresponds to a target superheat of 5°C (calibration value 8). This calibration value, used to maintain a low superheat at the evaporator's outlet, is determined based on the uniformity of the evaporator's outlet air temperature and system performance, and ranges from 4-8°C.

[0088] Step 370: Determine the target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack.

[0089] Among them, the process of determining the target opening of the third electronic expansion valve can refer to the above embodiment and will not be repeated here. Furthermore, when the thermal management system of this embodiment is applied to new energy vehicles, the control method of this embodiment is applicable when the temperature inside the vehicle is stable. The control method of this embodiment can make the outlet superheat of the battery pack basically maintain 0°C, the temperature uniformity of the battery pack is optimal, and it is suitable for the inlet and outlet temperature control of the battery pack after the system is stable. It can also avoid the problem of excessive outlet superheat of the battery pack under low load conditions when simply controlling the supercooling degree, and the continuous overheating of the battery pack outlet at 5-8°C when simply controlling the outlet superheat of the battery pack.

[0090] In one embodiment, reference Figure 2 The water circuit includes an armature assembly 201, an electronic water pump 202, a radiator 203, and a cooling fan 204. The third end of the water-cooled heat exchanger 40, the armature assembly 201, the electronic water pump 202, the radiator 203, and the fourth end of the water-cooled heat exchanger 40 are connected in sequence. The cooling fan 204 is located on one side of the radiator 203; the cooling fan 204 is electrically connected to the controller. The controller is also used to control the speed of the cooling fan and the compressor: the control target of the compressor speed is the minimum value of the target evaporation temperature in the cabin and the target evaporation temperature of the battery pack, that is, min(target evaporation temperature in the cabin, target evaporation temperature of the battery pack). The compressor automatically adjusts the speed using a PID algorithm so that the evaporation temperature at the evaporator outlet, i.e., the value collected by the pressure temperature sensor PT1, reaches min(target evaporation temperature in the cabin, target evaporation temperature of the battery pack), thereby simultaneously meeting the evaporation temperature requirements of the battery pack and the cabin. The speed of the cooling fan 204 and the electronic water pump 202 is based on the pressure table collected by the pressure temperature sensor PT2.

[0091] Fault handling: To mitigate the impact of abnormal overheating at the battery pack outlet caused by a small opening of the expansion valve in the system or a refrigerant shortage in the system, the control logic of the cooling fan and compressor is increased. When the overheating of the first end of the battery pack 70 is greater than the preset overheating threshold, and the first electronic expansion valve 61 fails or the opening of the first electronic expansion valve 61 reaches the preset opening threshold, the speed of the cooling fan 204 is controlled to increase. When the speed of the cooling fan 204 increases to the preset speed threshold, the opening of the third electronic expansion valve 63 is controlled to decrease. When the opening of the third electronic expansion valve 63 decreases to the preset opening threshold (calibrated value 10, initially set to 5%), the speed of the compressor 10 is controlled to decrease. The compressor 10 stops when the speed reaches the minimum allowable speed. To mitigate the impact of excessive temperature on the battery pack caused by the expansion valve in the system being in a large opening position, which results in the inlet refrigerant of the battery pack not being throttled and reduced in pressure, the control logic of the cooling fan and compressor is increased. The fan speed is first increased, and then the compressor speed is reduced. The compressor stops when the compressor reaches the minimum speed. A sensor that is strongly related to battery pack cooling fails, the inlet and outlet status of the battery pack is unpredictable, and the compressor cannot be turned on to protect the battery pack.

[0092] For example, Figure 5 This is a schematic diagram of the opening and flow provided by the third embodiment of the present invention. Figure 2 and Figure 5 The first, third, and fourth electronic expansion valves 61, 63, and 64 are large-diameter electronic expansion valves. When fully open, they function as solenoid valves. Their flow rate curves have two sections (46.9% is the dividing point). The first section is generally used for throttling expansion of liquid refrigerant, while the second section is generally used for regulating the pressure of gaseous refrigerant. When using PID automatic control, the opening of the first electronic expansion valve 61 is in the first section, and the opening of the third electronic expansion valve 63 is in the second section.

[0093] It should be noted that the specific size of each preset threshold in this embodiment can be determined according to actual control requirements and is not limited here.

[0094] The battery pack temperature control method of the thermal management system provided in this embodiment controls the opening of each electronic expansion valve to control the refrigerant flow rate flowing through each electronic expansion valve, and further controls the refrigerant flow rate entering and flowing out of the battery pack and the evaporation temperature of the battery pack, thereby controlling the outlet superheat of the battery pack, preventing excessive temperature difference between the inlet and outlet of the battery pack due to excessive overheating of the battery pack outlet, and preventing condensation in the battery pack and pipelines due to excessively low evaporation temperature of the battery pack.

[0095] Example 4

[0096] Figure 7This is a structural block diagram of a battery pack temperature control device of a thermal management system provided by the fourth embodiment of the present invention. The device is integrated into the controller of the thermal management system. The specific structure of the thermal management system is as follows Figure 2 and Figure 4 As shown, the specific description can refer to the above embodiment, which will not be repeated here. Figure 7 The device includes: a parameter acquisition module 410, a parameter determination module 420, and an opening determination module 430. The parameter acquisition module 410 is used to obtain the temperature and pressure of the second end of the water-cooled heat exchanger, the temperature and pressure of the first end of the battery pack, and the temperature and pressure of the evaporator outlet; the current operating mode of the thermal management system is the battery and cabin dual cooling mode; the parameter determination module 420 is used to determine the second end subcooling of the water-cooled heat exchanger, the first end superheat of the battery pack, and the outlet superheat of the evaporator based on the second end temperature and pressure of the water-cooled heat exchanger, the first end temperature and pressure of the battery pack, and the evaporator outlet temperature and pressure; the opening determination module 430 is used to determine the target opening of each electronic expansion valve based on the first end pressure, second end subcooling, first end superheat, and outlet superheat of the battery pack to control the temperature of the battery pack.

[0097] Based on the above embodiment, the opening determination module 430 includes:

[0098] a first control unit, configured to determine a superheat difference between the first-end superheat and the target superheat based on the first-end superheat and the target superheat, and perform PID control on the superheat difference to obtain a target opening of the first electronic expansion valve;

[0099] a second control unit, configured to determine a subcooling difference between the second end subcooling degree and the target subcooling degree based on the second end subcooling degree and the target subcooling degree, and perform PID control on the subcooling difference to obtain a target opening degree of the second electronic expansion valve;

[0100] The third control unit is configured to determine a target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack.

[0101] In one embodiment, the opening determination module 430 includes:

[0102] a fourth control unit, configured to determine a superheat difference between the first-end superheat and the target superheat based on the first-end superheat and the target superheat, and perform PID control on the superheat difference to obtain a first opening of the first electronic expansion valve;

[0103] a fifth control unit, configured to determine a subcooling difference between the second-end subcooling degree and the target subcooling degree based on the second-end subcooling degree and the target subcooling degree, and perform PID control on the subcooling difference to obtain a second opening degree of the first electronic expansion valve;

[0104] a sixth control unit, configured to determine a target opening of the first electronic expansion valve according to the first opening and the second opening;

[0105] a seventh control unit, configured to determine a superheat difference between the outlet superheat and the target superheat based on the outlet superheat and the target superheat, and perform PID control on the superheat difference to obtain a target opening of the second electronic expansion valve;

[0106] An eighth control unit is configured to determine a target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack.

[0107] Optionally, the sixth control unit includes:

[0108] a first control subunit, configured to use the first opening as a target opening of the first electronic expansion valve if the first opening is greater than the second opening;

[0109] The second control subunit is configured to use the second opening degree as a target opening degree of the first electronic expansion valve if the first opening degree is less than or equal to the second opening degree.

[0110] Optionally, the third control unit and the eighth control unit are specifically used to determine the evaporation temperature of the first end of the battery pack based on the pressure of the first end of the battery pack; if the target evaporation temperature in the cabin is lower than the target evaporation temperature of the battery pack, the temperature difference is obtained by subtracting the first end evaporation temperature from the target evaporation temperature of the battery pack; the temperature difference is PID controlled to obtain the target opening of the third electronic expansion valve; if the target evaporation temperature in the cabin is higher than or equal to the target evaporation temperature of the battery pack, the target opening of the third electronic expansion valve is controlled to be a preset maximum opening.

[0111] Optionally, the water circuit includes an armature assembly, an electronic water pump, a radiator and a cooling fan, the third end of the water-cooled heat exchanger, the armature assembly, the electronic water pump and the radiator are connected in sequence, and the cooling fan is located on one side of the radiator; the cooling fan is electrically connected to the controller; the opening determination module 430 is also used to, after determining the target opening of the first electronic expansion valve and the second electronic expansion valve, when the overheat of the first end of the battery pack is greater than a preset overheat threshold, and the first electronic expansion valve fails or the opening of the first electronic expansion valve reaches a preset opening threshold, control the speed of the cooling fan to increase; when the speed of the cooling fan increases to the preset speed threshold, control the opening of the third electronic expansion valve to decrease; when the opening of the third electronic expansion valve decreases to the preset opening threshold, control the speed of the compressor to decrease.

[0112] The battery pack temperature control device of the thermal management system provided in this embodiment and the battery pack temperature control method of the thermal management system provided in any embodiment of the present invention belong to the same inventive concept and have corresponding beneficial effects. For technical details not detailed in this embodiment, please refer to the battery pack temperature control method of the thermal management system provided in any embodiment of the present invention.

[0113] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations, and substitutions are possible for those skilled in the art without departing from the scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A battery pack temperature control method for a thermal management system, characterized in that: The thermal management system includes a refrigerant circuit, a water circuit and a controller. The refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger, and the first end of the battery pack is connected to the gas-liquid separator The inlet of the battery pack is connected, the outlet of the gas-liquid separator is connected to the inlet of the compressor, the first electronic expansion valve is located in a pipeline connected to the second end of the battery pack and is close to the second end of the battery pack, the second electronic expansion valve is located in a pipeline connected to the inlet of the evaporator and is close to the inlet of the evaporator, the third electronic expansion valve is located in a pipeline connected to the first end of the battery pack and is close to the first end of the battery pack, the third end and the fourth end of the water-cooled heat exchanger are connected to the water circuit; the compressor and each electronic expansion valve are electrically connected to the controller, and the control method is executed by the controller, and the control method includes: Obtaining the temperature and pressure of the second end of the water-cooled heat exchanger, the temperature and pressure of the first end of the battery pack, and the temperature and pressure of the evaporator outlet; the current operating mode of the thermal management system is a dual cooling mode for the battery and cabin; determining a subcooling degree at the second end of the water-cooled heat exchanger, a superheat degree at the first end of the battery pack, and a superheat degree at the outlet of the evaporator based on the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the outlet of the evaporator; determining a target opening of each electronic expansion valve according to the pressure at the first end of the battery pack, the subcooling degree at the second end, the superheat degree at the first end, and the outlet superheat degree, so as to control the temperature of the battery pack; The determining the target opening of each electronic expansion valve according to the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree, and the outlet superheating degree includes: determining a superheat difference between the first end superheat and the target superheat according to the first end superheat and the target superheat, and performing PID control on the superheat difference to obtain a target opening of the first electronic expansion valve; determining a subcooling difference between the second end subcooling degree and the target subcooling degree according to the second end subcooling degree and the target subcooling degree, and performing PID control on the subcooling difference to obtain a target opening degree of the second electronic expansion valve; A target opening of the third electronic expansion valve is determined according to the pressure at the first end of the battery pack.

2. The control method according to claim 1, characterized in that: The determining the target opening of each electronic expansion valve according to the first end pressure of the battery pack, the second end subcooling degree, the first end superheating degree, and the outlet superheating degree includes: determining a superheat difference between the first end superheat and the target superheat according to the first end superheat and the target superheat, and performing PID control on the superheat difference to obtain a first opening of the first electronic expansion valve; determining a subcooling difference between the second end subcooling degree and the target subcooling degree according to the second end subcooling degree and the target subcooling degree, and performing PID control on the subcooling difference to obtain a second opening degree of the first electronic expansion valve; determining a target opening of the first electronic expansion valve according to the first opening and the second opening; determining a superheat difference between the outlet superheat and the target superheat according to the outlet superheat and the target superheat, and performing PID control on the superheat difference to obtain a target opening of the second electronic expansion valve; A target opening of the third electronic expansion valve is determined according to the pressure at the first end of the battery pack.

3. The control method according to claim 2, characterized in that: Determining a target opening of the first electronic expansion valve according to the first opening and the second opening includes: If the first opening is greater than the second opening, the first opening is used as the target opening of the first electronic expansion valve; If the first opening degree is less than or equal to the second opening degree, the second opening degree is used as the target opening degree of the first electronic expansion valve.

4. The control method according to claim 1 or 2, characterized in that: The determining the target opening of the third electronic expansion valve according to the first end pressure of the battery pack includes: determining an evaporation temperature at a first end of the battery pack according to a pressure at a first end of the battery pack; If the target evaporation temperature in the cabin is lower than the target evaporation temperature of the battery pack, subtracting the first end evaporation temperature from the target evaporation temperature of the battery pack to obtain a temperature difference; Performing PID control on the temperature difference to obtain a target opening of the third electronic expansion valve; If the target evaporation temperature in the cabin is higher than or equal to the target evaporation temperature of the battery pack, the target opening of the third electronic expansion valve is controlled to be a preset maximum opening.

5. The control method according to claim 1, characterized in that: The water circuit includes an armature assembly, an electronic water pump, a radiator and a cooling fan. The third end of the water-cooled heat exchanger, the armature assembly, the electronic water pump and the radiator are connected in sequence. The cooling fan is located on one side of the radiator. The cooling fan is electrically connected to the controller. After determining the target opening degrees of the first electronic expansion valve and the second electronic expansion valve, the method includes: When the overheat degree of the first end of the battery pack is greater than a preset overheat threshold, and the first electronic expansion valve fails or the opening degree of the first electronic expansion valve reaches a preset opening degree threshold, controlling the speed of the cooling fan to increase; When the speed of the cooling fan increases to a preset speed threshold, controlling the opening of the third electronic expansion valve to decrease; When the opening degree of the third electronic expansion valve decreases to a preset opening degree threshold, the speed of the compressor is controlled to decrease.

6. The control method according to claim 1, characterized in that: The refrigerant circuit further includes a fourth electronic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve and a fourth solenoid valve, the fourth electronic expansion valve being located in a pipeline connected to the outlet of the condenser and close to the outlet of the condenser, the first solenoid valve being located in a pipeline connected to the outlet of the compressor and the first end of the water-cooled heat exchanger, the second solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the condenser, the third solenoid valve being located in a pipeline connected to the outlet of the evaporator and the first end of the water-cooled heat exchanger, and the fourth solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the gas-liquid separator; each solenoid valve and each electronic expansion valve being electrically connected to the controller; In the battery and cabin dual cooling mode, the first solenoid valve and the fourth solenoid valve are turned on, the second solenoid valve, the third solenoid valve and the fourth electronic expansion valve are turned off.

7. A battery pack temperature control device for a thermal management system, characterized in that: The thermal management system includes a refrigerant circuit, a water circuit and a controller. The refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger, and the first end of the battery pack is connected to the gas-liquid separator The inlet of the battery pack is connected to the inlet of the gas-liquid separator, the outlet of the gas-liquid separator is connected to the inlet of the compressor, the first electronic expansion valve is located in a pipeline connected to the second end of the battery pack and is close to the second end of the battery pack, the second electronic expansion valve is located in a pipeline connected to the inlet of the evaporator and is close to the inlet of the evaporator, the third electronic expansion valve is located in a pipeline connected to the first end of the battery pack and is close to the first end of the battery pack, and the third and fourth ends of the water-cooled heat exchanger are connected to the water circuit; the compressor and each electronic expansion valve are electrically connected to the controller, and the control device is integrated in the controller; the control device includes: a parameter acquisition module, configured to acquire the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the evaporator outlet; wherein the current operating mode of the thermal management system is a dual cooling mode for the battery and the cabin; a parameter determination module, configured to determine a subcooling degree at the second end of the water-cooled heat exchanger, a superheat degree at the first end of the battery pack, and an outlet superheat degree of the evaporator based on the temperature and pressure at the second end of the water-cooled heat exchanger, the temperature and pressure at the first end of the battery pack, and the temperature and pressure at the outlet of the evaporator; an opening determination module, configured to determine a target opening of each electronic expansion valve based on the pressure at the first end of the battery pack, the subcooling degree at the second end, the superheat degree at the first end, and the outlet superheat degree, so as to control the temperature of the battery pack; The opening determination module includes: a first control unit, configured to determine a superheat difference between the first-end superheat and the target superheat based on the first-end superheat and the target superheat, and perform PID control on the superheat difference to obtain a target opening of the first electronic expansion valve; a second control unit, configured to determine a subcooling difference between the second-end subcooling degree and the target subcooling degree based on the second-end subcooling degree and the target subcooling degree, and perform PID control on the subcooling difference to obtain a target opening degree of the second electronic expansion valve; The third control unit is configured to determine a target opening of the third electronic expansion valve according to the pressure at the first end of the battery pack.

8. A thermal management system, characterized in that: include: A refrigerant circuit, a water circuit and a controller, wherein the refrigerant circuit includes a compressor, a condenser, an evaporator, a water-cooled heat exchanger, a gas-liquid separator, a first electronic expansion valve, a second electronic expansion valve, a third electronic expansion valve and a battery pack; the outlet of the compressor is connected to the first end of the water-cooled heat exchanger, the inlet of the condenser and the first end of the battery pack, the second end of the water-cooled heat exchanger is connected to the outlet of the condenser, the outlet of the condenser is connected to the inlet of the evaporator and the second end of the battery pack, the outlet of the evaporator is connected to the first end of the battery pack and the first end of the water-cooled heat exchanger, the first end of the battery pack is connected to the inlet of the gas-liquid separator The outlet of the gas-liquid separator is connected to the inlet of the compressor, the first electronic expansion valve is located in a pipeline connected to the second end of the battery pack and is close to the second end of the battery pack, the second electronic expansion valve is located in a pipeline connected to the inlet of the evaporator and is close to the inlet of the evaporator, the third electronic expansion valve is located in a pipeline connected to the first end of the battery pack and is close to the first end of the battery pack, the third end and the fourth end of the water-cooled heat exchanger are connected to the water circuit; the compressor and each electronic expansion valve are electrically connected to the controller, and the control device according to claim 7 is integrated into the controller.

9. The thermal management system according to claim 8, characterized in that: The refrigerant circuit further includes a fourth electronic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve and a fourth solenoid valve, the fourth electronic expansion valve being located in a pipeline connected to the outlet of the condenser and close to the outlet of the condenser, the first solenoid valve being located in a pipeline connected to the outlet of the compressor and the first end of the water-cooled heat exchanger, the second solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the condenser, the third solenoid valve being located in a pipeline connected to the outlet of the evaporator and the first end of the water-cooled heat exchanger, and the fourth solenoid valve being located in a pipeline connected to the first end of the battery pack and the inlet of the gas-liquid separator; each solenoid valve and each electronic expansion valve being electrically connected to the controller; The water circuit includes an armature assembly, an electronic water pump, a radiator and a cooling fan. The third end of the water-cooled heat exchanger, the armature assembly, the electronic water pump, the radiator and the fourth end of the water-cooled heat exchanger are connected in sequence. The cooling fan is located on one side of the radiator; the cooling fan is electrically connected to the controller.

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